In the specification R12 (Release 12) of the Third Generation Partnership Project (3GPP), the concept of dual connectivity is introduced for Long Term Evolution (LTE) technology. That is, two base stations of LTE (for example, evolved Node B, ENB) perform uplink and downlink data transmission with a user equipment (UE) through collaboration. One of the two base stations is a master base station which maintains radio resource control (RRC) signaling of the UE and configures measurement configuration of the UE, and the other base station is a secondary base station which is only responsible for data transmission. When the UE performs inter-frequency measurement, the master base station needs to configure a measurement gap (referred to as GAP hereinafter) for the UE. The UE interrupts communication with all current serving cells during the Gap, to tune its radio frequency (RF) to target inter frequency to be measured and to measure synchronization signals and specific reference signals of neighboring cells at the inter frequency. Therefore, in the dual connectivity of LTE, although the UE generally includes two RF transceivers, the communication between the UE and the master and secondary base stations is interrupted during the GAP, and the UE can perform inter-frequency measurement with any one of the two RF transceivers.
In the recently developed new radio (NR, named as 5G) technology, the concept of LTE-NR dual connectivity (EN DC) is introduced. For example, eNB of LTE serves as the master base station (i.e., master node, MN), gNB of NR serves as the secondary base station (i.e., secondary node, SN), where the gNB as the secondary base station can also configure RRC signaling and exchange RRC signaling directly with the UE. If the master base station and the secondary base station configure their own NR measurement configuration independently, an NR measurement function needs to be added into an LTE baseband circuit of the UE, which is a great change for the UE, and unfavorable to practical applications. Besides, as existing specifications do not specify how the master base station (for example, eNB) and the secondary base station (for example, gNB) cooperate to configure a GAP for the inter-frequency measurement. If the existing solution where the master base station configures the GAP to be applied to all the serving cells is followed, a long period of service interruption may be caused, and communication experience of the UE may be affected.